How can I dock my button in each TableRow fill in TableLayout from top to bottom in Android?

How can I dock my button in each TableRow fill in TableLayout from top to bottom in Android?

Here's my layout code:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://ift.tt/nIICcg"
xmlns:tools="http://ift.tt/LrGmb4"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".Main" >

<RelativeLayout
    android:id="@+id/relativeLayout1"
    android:layout_width="wrap_content"
    android:layout_height="40dp"
    android:layout_alignParentLeft="true"
    android:layout_alignParentRight="true"
    android:layout_alignParentTop="true"
    android:background="@color/red_color" >
</RelativeLayout>

<EditText
    android:id="@+id/editText1"
    android:layout_width="wrap_content"
    android:layout_height="100dp"
    android:layout_alignParentLeft="true"
    android:layout_alignParentRight="true"
    android:layout_below="@+id/relativeLayout1"
    android:ems="10"
    android:background="@color/blue_color"
    android:inputType="text" >

    <requestFocus />
</EditText>

<TableLayout
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:layout_alignParentBottom="true"
    android:layout_alignParentLeft="true"
    android:layout_alignParentRight="true"
    android:layout_below="@+id/editText1" >

    <TableRow
        android:id="@+id/tableRow1"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent" >

        <Button
            android:id="@+id/btn1"
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"
            android:layout_weight="1"
            android:text="@string/_1"
            android:onClick="onEqual"
            android:textSize="20sp" />
        <Button
            android:id="@+id/btn2"
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"
            android:layout_weight="1"
            android:text="@string/_2"
            android:onClick="onEqual"
            android:textSize="20sp" />
        <Button
            android:id="@+id/btn3"
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"
            android:layout_weight="1"
            android:text="@string/_3"
            android:onClick="onEqual"
            android:textSize="20sp" />
    </TableRow>

    <TableRow
        android:id="@+id/tableRow2"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent" >

        <Button
            android:id="@+id/btn4"
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"
            android:layout_weight="1"
            android:onClick="onEqual"
            android:text="@string/_4"
            android:textSize="20sp" />

        <Button
            android:id="@+id/btn5"
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"
            android:layout_weight="1"
            android:text="@string/_5"
            android:onClick="onEqual"
            android:textSize="20sp" />
        <Button
            android:id="@+id/btn6"
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"
            android:layout_weight="1"
            android:text="@string/_6"
            android:onClick="onEqual"
            android:textSize="20sp" />
    </TableRow>

    <TableRow
        android:id="@+id/tableRow3"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent" >
        <Button
            android:id="@+id/btn7"
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"
            android:layout_weight="1"
            android:text="@string/_7"
            android:onClick="onEqual"
            android:textSize="20sp" />
        <Button
            android:id="@+id/btn8"
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"
            android:layout_weight="1"
            android:text="@string/_8"
            android:onClick="onEqual"
            android:textSize="20sp" />
        <Button
            android:id="@+id/btn9"
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"
            android:layout_weight="1"
            android:text="@string/_9"
            android:onClick="onEqual"
            android:textSize="20sp" />
    </TableRow>

    <TableRow
        android:id="@+id/tableRow4"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent" >
        <Button
            android:id="@+id/btnBackSpace"
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"
            android:layout_weight="1"
            android:onClick="onEqual"
            android:textSize="20sp" />
        <Button
            android:id="@+id/btn0"
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"
            android:layout_weight="1"
            android:text="@string/_0"
            android:onClick="onEqual"
            android:textSize="20sp" />

        <Button
            android:id="@+id/btnEnter"
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"
            android:layout_weight="1"
            android:onClick="onEqual"
            android:textSize="20sp" />

    </TableRow>
</TableLayout>

Actually, my buttons in each TableRow can dock from left to right properly, but I don't know how I can dock it from top to bottom in order to fill each TableRow in TableLayout.